Aluminum. Upper part of drum that rides on roller bearings, check. Have access to machine shop. Winches are rare old Lewmar single speed 30ST. I have four from my IOR winch farm. I am probably going to sell them and want an answer if someone get that deep upon examination. They don’t rattle or wobble. Drum wall seems to be about 3/16 to 1/4 thick.
Maybe use a cylinder hone on the drum interior to smooth it out. Then heat the drum, freeze these in dry ice, and then insert into drum. Designed to repair all sorts of shafts and come in a huge range of sizes. 304 s.s. There are many makers of these so look around to get exact size you need. Measure inside dia. of drum with an inside micrometer.